Pokemon Go vibrating too often since last update (0.49.1)

Since the last update of Pokemon Go (6 December, Android 0.49.1) my game vibrates too often. It is exactly like the 'new-Pokemon-on-the-map', but there are actually no new Pokemon. Is this intended with the new update

It is not because I got another notification, because they all get sent to my wristband, my phone only vibrates on in-game vibrations.

This bug has been fixed as of the latest update, 0.51.0 Android/1.21.0 iOS

The bug that caused incorrect vibration notifications has been fixed.

According to this thread it is most likely a bug that causes vibrating whenever Nearby (not Sightings) list updates.

Update: Niantic confirmed that it is a bug.